For a long time now, we've been talking about partisan divisions between Republicans and Democrats. They're at odds over everything from how to fix health care to how to fight terrorism. But there is one thing they can agree on.

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JOE BIDEN: My name is Joe Biden, and I love ice cream.

NANCY PELOSI: Chocolate is good for your teeth. It's my cup of coffee.

JOHN KASICH: Wherever I get ice cream, I'm all in favor.

BARACK OBAMA: I'm going to go for the classic mint chocolate chip.

MARTIN: Of course, that was former Vice President Joe Biden, House Democratic leader Nancy Pelosi, Ohio Governor John Kasich and former President Barack Obama. So on this Fourth of July weekend, we wanted to take a few minutes to look back on how ice cream became one of America's most popular treats, to the tune of some 45 pints per person per year on average. Journalist Amy Ettinger told us all about it in a piece in The Washington Post last week titled "How Ice Cream Went From Elitist Indulgence To America's Favorite Frozen Treat." It turns out that the Founding Fathers had a lot to do with that. Amy Ettinger is with us now from San Francisco to tell us more. Hi, Amy, welcome. Happy Fourth.

AMY ETTINGER: Hi. Thank you.

MARTIN: So you were telling us in your piece that George Washington is one of the people who sparked the country's fondness for ice cream. Tell us about it.

ETTINGER: So he had an absolute sweet tooth, as we all know. It turns out his real love was for ice cream. He was introduced to it around 1768 or 1770, and then he became an addict. He started serving it at Mount Vernon all the way back in 1784. And when they did a catalog of his possessions, he had a 306-piece ice cream serving set. So it was just such a large part of Martha and George's life.

MARTIN: So which of our other presidents were fans of ice cream?

ETTINGER: So Thomas Jefferson, when he was in France, he became quite the foodie. And he actually recorded America's first ice cream recipe, which was an 18-step process that included hand churning the ice cream for 10 minutes. So it was quite a labor, but he really spared no expense to be able to get this treat. He had ice houses built at his estate at Monticello, and he was able to serve it year-round because of that.

MARTIN: Well, in fact, that is part of the tour at Monticello is, you know, you get to see the icehouses. And so you get a sense of just how much he really liked that. But that suggests that you really had to have some resources in order to enjoy ice cream at one point. So how did it go from something that only a select few could enjoy to something that is everywhere?

ETTINGER: The ice trade really took off in the, you know, late-18th, early-19th century. And this enabled folks to be able to more easily have access to ice. And that was, of course, key in being able to make ice cream.

MARTIN: And you were also telling us that the passion for ice cream reached a new intensity during prohibition. How did that work?

ETTINGER: So people needed an alternative vice (laughter). They couldn't have their booze, and the Temperance Movement actually was pushing ice cream parlors as an alternative to the saloon. So in 1920, our nation's first year without alcohol, consumers ate 260 millions gallons of ice cream.

MARTIN: Before we let you go, what made you want to do so much research into this and even write a book about it?

ETTINGER: I have always loved ice cream. And I remember eating it all the time as a kid. And when I started doing the research, I saw, well, it doesn't just go back to my own personal childhood, it goes back to the birth of the country. And I wanted to research that, be able to bring that history and make it come alive with my own memories of having it as a kid and talking to all the folks around the country who are making it and serving it every day.

MARTIN: That's Amy Ettinger. She's a journalist and author of the new book "Sweet Spot: An Ice Cream Binge Across America." She joined us from San Francisco. Amy, thanks so much for speaking with us. We hope you have a sweet Fourth.